1. Field of the Invention
The present invention is applicable to the fields of fitness, exercise, physical rehabilitation, sports medicine and extremity testing and is directed to methods and apparatuses useable in such fields.
2. Description of the Related Art
Numerous devices have been developed to increase the strength, agility and quickness of athletes and other persons. In addition to enhancing the performance of athletes, such devices are used to improve or maintain the fitness and health of non-athletes, both to enhance the lifestyles of non-athletes and to potentially increase their respective life spans. Such devices range from basic equipment such as barbells, dumbbells, and the like, to increasingly more complex equipment such as universal gyms which enable a user to quickly modify the weights or resistances being used to exercise the user's muscles. See, for example, U.S. Pat. Nos. 4,257,593, 5,526,692 and 5,336,145 to Dennis L. Keiser and U.S. patent application Publication No. US 2002/0024590 A1, which describe exercising apparatuses and related devices using pneumatic devices to provide controllable resistances, and which are incorporated by reference herein. In particular, such pneumatic exercising apparatuses advantageously reduce or eliminate the inertial effects of conventional weights wherein the force required to start moving a weight and the tendency of the weights to continue moving cause the forces required during each exercising stroke to vary throughout the stroke. Such pneumatic apparatuses provide a generally constant resistance throughout the exercising stroke.
In addition to being used for the development of strength, agility and quickness, exercising apparatuses can be used to measure strength, agility and quickness of a person. For example, a person's ability to lift weights against the force of gravity or a corresponding ability to move against a resistance can be measured at different times to determine whether such characteristics are improving in response to an exercise program or in response to therapy. Such measurements can also be used for evaluation purposes to determine whether one or more muscles or muscle groups are not performing adequately so that a therapist or a fitness trainer, for example, can develop a program of therapy or training more specifically directed to the inadequately performing muscles.
Historically, measurement and evaluation of muscular performance have concentrated on measuring the strength of a muscle or muscle group (e.g., measuring the amount of weight that can be lifted). However, it has been determined that strength alone does not accurately represent the performance of muscles. A person's muscles may be able to lift an adequate amount of weight, but may be too slow to be useful for many purposes. For example, an athlete putting the shot at a track and field contest must have the strength to easily move the sixteen-pound shot; however, the strength must be coupled with sufficient speed to cause the shot to be propelled with enough velocity to travel in excess of 70 feet (e.g., 70 feet, 11.25 inches by Randy Bames at the 1996 Atlanta Olympics). In contrast, some activities require the ability to move very heavy objects at much lower velocities. Thus, although the power requirements may be similar for two activities, the forces and velocities at which the maximum power is required may be different for the two activities.
From the foregoing it should be understood that a more meaningful measurement of the performance of a person's muscles is a measurement of power (e.g., a measurement of the force applied by the muscles times the velocity of the movement). The average power over an exercise stroke, for example, can be accomplished by timing the duration of the stroke and measuring the distance traveled to determine the average velocity, and then multiplying the average velocity by the force (e.g., the weight moved or the resistance overcome by the muscles). However, because of the structure of most appendages in a person's body, the speed of an exercise stroke will vary throughout the stroke as the appendage varies from full extension to full contraction and the leverage of the muscles against the moving portion of the appendage changes.